Numerical Analysis Applied to the Taxonomy of the Genus Valantia L

NUMERICAL ANALYSIS APPLIED TO THE TAXONOMY OF THE GENUS VALANTIA L. (RUBIACEAE)

by MARIO AIELLO, SALVATORE BRULLO & VINCENZO PICCIONE *

Abstract AIELLO, M., S BRULLO & V. PICCIONE (1981). Numerical analysis applied to the taxonomy of the genus Valantia L. (Rubiaceae). Actas III Congr. ÓPTIMA. Anales Jard. Bot. Madrid 37(2): 577-586. On the basis of the diacritic characters of the fructiferous corpus a numerical analysis on the Valantia species was made. The object of this research is to verify the taxonomic relationships among the 6 known species by cluster analysis, above all in consequence of the recent discovery of two new species. For each species 20 fructiferous corpora were examined and 22 characters of them were taken into consideration. The similarity measurements calculated among all the pairs of OTU's are reported on a matrix to which the cluster analysis was applied. The results confirm the validity of the specific rank given to the 6 taxa of Valantia and the primary importance of the diagnostic valué of the fructiferous corpus morphology.

Resumen AIELLO, M., S. BRULLO & V. PICCIONE (1981). Análisis numérico aplicado a la taxonomía del género Valantia L. (Rubiaceae). Actas III Congr. ÓPTIMA. Anales Jard. Bot. Madrid 37(2): 577-586 (En inglés). Basándose en caracteres diacríticos de las fructificaciones se realiza un análisis numérico de las especies de Valantia. El objetivo de esta investigación es verifi- car las relaciones taxonómicas por medio del análisis de agregación entre las seis especies conocidas, especialmente después del reciente descubrimiento de dos nuevas especies. Para cada especie fueron examinadas 20 fructificaciones y de cada fructificación se consideraron 22 caracteres. Las medidas de similitud calcu- ladas entre todos los pares de OTU se presentan en una matriz a la que se le aplicó el análisis de agragación. Los resultados confirman la validez del rango específico dado a los 6 táxones de Valantia y la importancia del valor diagnóstico de la morfología de las fructificaciones.

(•) Istituto di Botánica, Universitá di Catania, Via A. Longo, 19. 95125 Catania, Ita- lia. 578 ANALES JARDÍN BOTÁNICO DE MADRID, 37 (2) 1981

INTRODUCTION

The genus Valantia is differentiated from the remainder of the Rubia- ceae because of the presence of a very peculiar inflorescence and fructiferous corpus. The taxonomical importante and the diagnostic valué of these parts of the plant were already put in evidence by LINNÉ (1753) who, because of this, founded a distinct genus. Previously, various authors interested themselves in taxonomic añinities and phylogenesis of the genus Valantia; among which: BALDACCI (1893), FAGERLIND (1937), EHRENDORFER (1970). Due to the recent discovery of two new species of Valantia (BRU- LLO, 1979, 1980), the systematic position of each taxa has been brought up to discussion again. Therefore, we have thought it better to verify the relationships that are existing among the 6 taxa known, on the basis of the morphological characters of the fructiferous corpus. We have chosen this part of the plant because it represents the most important diagnostic character in orden to hierarchize at a specific level (Fig. 1), In order to quantify better the diversities observed among the fructiferous corpora of the single taxa, methods of numerical analysis were used. In this way, the limits among the various taxa and their relationships can be specified objectively. The cluster analysis according to SOKAL & SNEATH (1963, 1973) was applied to the data subjected to GoWER's (1971) coefficient of similarity. Besides, the arithmetical averages of the data have permitted to eviden- tiate the taxonomical distances occuring among the taxa.

MATERIAL

For this research, only herbarium specimens from the collection of the botanical museums of Catania (CAT), Palermo (PAL), Athens (ATH, ATHU) and Patras (UPA), were utilized. The fructiferous corpora were chosen among the ones that were more mature and that were in better conditions; not more than two fructiferous corpora have been examined for each herbarium specimen. For each taxon, 20 fructiferous corpora were examined for the numerical analysis; for each one, 22 characters relative to the phenotype were taken into consideration.

METHOD

For this study only the morphological characters of the fructiferous corpora were compared. Twenty two characters for each species were examined. The comparison was carried out on 120 OTU's (20 specimens for each taxa). GoWER's (1971) formula was applied to the data matrix of 120 OTU's and 22 characters. This estimates the similarities between the data measured by variables defined at different levéis of scale. Fig. 1. — Iconography of the fructiferous corpora of Valantia species: A) V. muralis L.; B) V. columella (Ehrenb. ex Boiss.) Baldacci; C) V. deltoidea Brullo; D) V. aprica (Sibth. & Sm.) Boiss. & Heldr.; E) V. hispida L.; F) V. calva Brullo. 580 ANALES JARDÍN BOTÁNICO DE MADRID, 37 (2) 1981

The cluster analysis was applied to the results and the method used is the average linkage dustering with process WVGM (weighted variable-group method). A brief description is given. It isolates the pairs of OTU's with a smaller taxonomic distance. These will constitute the initial groups. Then, the distance between every OTU and the initial group is calculated. This procedure is repeated by first recalculating the matrix until all the OTU's are reduced to only one group. The OTU's (or groups of OTU's) are placed in position in the abscissa of a dendrogam and the correlation coefíicient scale is placed in the ordinate. The arithmetic average of the data relative to the fructiferous corpora of each species was made and through GoWER's formula, a matrix was obtained and it represents the absolute taxonomical distances among the 6 species. The numerical valúes are reported in Fig. 3 in the shape of a triangular semi-matrix (1).

B C P E F j 0.462 0.613 0.401 0.547 0.534 A 0.341 0.378 0.638 0.550 B 0.485 0.583 0.629 C 0.355 0.448 D 0.550 E

A-V. muralis B-V. calva C- V. columella D - V. deltoidea E- V. hispida F — V. aprica

Fig. 3. — The upper part of the matrix of GOWER'S (1971) general coeilicient. The valúes are complemented at 1.

RESULTS

The phenogram of Fig. 2 places each taxon in a distinct cluster. In every cluster the variability is very low and is included between 1.00 and 0.89 phenon level. The highest homogeneity is found in V. columella,

(1) For computing procedure the CDC-6600 System of Data Center at the University of Catania (Italy) is used. The programs are written in FORTRAN IV by AlELLO and PlCCIONE. Fig. 2. — Dendrogram of the relationships among 120 OTU's, based on the WPGM cluste- ring method. 582 ANALES JARDÍN BOTÁNICO DE MADRID, 37 (2) 1981

whilst the highest variability is found in V. aprica. The first cluster that separates itself at 0.67 phenon level is the one relative to V. columella, whilst the last two clusters that sepárate themselves at a 0.77 phenon level are the ones of V. calva and V. muralis. In other words, the separa- tion of all the clusters occurs between two phenon levéis which are quite near. Therefore, the degree of diversity among the 6 taxa is high and this ratifies their differentiations at a specific rank according to the systematic which was used up to now.

Fig. 4. — 3-dimensional model of the taxonomic distances among 6 species of Valantia. The dimensions are the three largest principal component extracted from a trasformation of the distance matrix of Fig. 3. M. AIELLO & AL.: THE GENUS VA1LANTIA 583

In particular, GOWER' (1971) general coefficient aplied to the average valúes usted in Table 1, supplies us with the matrix of the taxonomical distance that exists among the 6 species. The tridimensional model of these distances visualized the relationships among the species on the basis of their position in space (Fig. 4, 5). Among, these, the most isolated is V. aprica which has few connections with the remaining species. Another species, that is quite isolated, is V. muralis which in a particular way shows a greater affinity with V. deltoideá and in a lesser way with V. calva, whilst it diíferentiates remarkably from the others. V. hispi-

Fig. 5. — 3-dimensional model as for Fig. 4, with projection of the vértices on the «x y» plañe surface.

M. AIELLO & AL.: THE GENUS VAILANTIA 585

da shows some affinities only with V. deltoidea. Even V. columella presents itself well isolated taxonomically and shows a greater affinity only with V. calva.

DlSCUSSION

These observations are to be found even in the considerations dedu- ced from the comparative analysis of the morphological characteristics of the fructiferous corpora and also from the observations regarding the habit, ecology, chorology and the caryological data. On the basis of this, V. aprica can be considered the most isolated taxonomically, since it is the only perennial species of the genus, and it is characterized by a rather narrow distribution (it is known only for some mountains of the S. Bal- kan and of Crete) and has a fructiferous corpus with peduncle and flowering pedicels not incrassate and briefly coalescent, and not enclosing the maricarp. In fact, the other species are always annual and have the fructiferous corpora with peduncle and flowering pedicels manifestly incrassate and coalescent, more or less enclosing the mericarp (or the mericarps). Among these, V. hispida and V. muralis have a wide pan- mediterranean distribution, whilst V. columella has a distribution limited to steppe countries in the C. E. North-África and they all have a fructiferous corpus well distinct morphologically. Finally, V. calva, endemic to the Island of Linosa, and V. deltoidea, endemic to Rocca Busambra (Sici- ly), have a very localized distribution; their fructiferous corpora, although very peculiar, have some affinities with those of V. muralis. Regarding the phylogenesis, we may suppose that V. aprica probably represents the most primitive taxon of the genus; in fact, from the morphology of its fructiferous corpus, from its habit and as it is the only species with a diploid chromosome complement with a basic number x = 11, it is the one that is more similar to the species of the genus Galium; therefore, it represents the taxon of connection between the two genera. The diploid annual species with x = 9, such as V. hispida and V. muralis have probably been originated by disploidy phenomena from a taxa with chromosome complement of 2n = 22. Instead, V. deltoidea and V. columella, both tetraploid, have probably originated through allopolyploidy processes; the former, with 2« = 36, would have originated by hybridation between two taxa with 2n = 18; whilst the latter, that has 2n = 40, would have originated from the hybridation through unreduced gamets between a taxon with 2n = 18 and one with 2n = 22. Finally, V. calva is undoubtedly a neo-endemism being localized on a small volcanic island with a post- pliocenic origin, which compared to other spacies of Valantia, presents a fructiferous corpus with the smallest dimensión and completely whithout bristles; it has probably originated itself from V. muralis by a series of mutations. On the basis of the morphological characters of the fructiferous corpus the following key is given: 586 ANALES JARDÍN BOTÁNICO DE MADRID, 37 (2) 1981

1. Fructiferous Corpus not incrassate, but only lightly canaliculate in the ventral part. Mericarp up to 2 mm long, ± enterely projecting V. aprica 1. Fructiferous corpus incrassate, with a deep ventral cavity. Mericarp up to 1.5 mm long, ± enclosed 2 2. Fructiferous corpus without any bristles V. calva 2. Fructiferous corpus always provided with bristles 3 3. Fructiferous corpus entirely covered by flat bristles which are up to 2 mm long V. columella 3. Fructiferous corpus partly covered by flat bristles which are up to 1.2 mm long 4 4. Fructiferous corpus hispid, with bristles 0.7-1.2 mm long, without dorsal coronule. Mericarps 2, papillose V. hispida 4. Fructiferous corpus glabrous with dorsal coronule and with bristles 0.2-0.7 mm long. Mericarp 1, smooth 5 5. Fructiferous corpus with dorsal subcylindric rostrum up to 2 mm long provided with an apical coronule of 6-15 bristles. Terminal horns with 2-12 bristles each V. muralis 5. Fructiferous corpus without or with a very short dorsal rostrum provided with an apical coronule of 2-5 bristles. Termi- nal horns with 0-5 bristles each V. deltoidea

BlBLIOGRAPHIC REFERENCES

BALDACCI, A. (1893). Osservazioni sulle Rptatae e particolarmente sul genere Vaillantia DC. Malpighia 7:203-208. BRULLO, S. (1979). Valantia calva, a new species from Linosa, Sicily. Bot. Not. 132:61-64. BRULLO, S. (1980). Valantia deltoidea, sp. nov. from Sicily. Bot. Not. 133:63-66. EHRENDORFER, F. (1970). Mediterran-mitteleuropáische Florenbeziehungen im Lichte cytota- xonomischer Befunde. Ftddes Ripert. 81:3-32. FAGERLIND, F. (1937). Embryologische, zytologische und bestáubungsex-perimentelle Studien in der Familie Rubiaceae nebst Bemerkungen über einige Polyploiditátsprobleme. Acta HortiBerg. 11 (9). GOWER, J. C. (1971). A general coeflicient of similarity and some of its properties. Biometrics 27:857-871. SNEATH, P. H. A. & R. R. SOKAL (1973). Numerical taxonomy. W. H. Freeman and Company (ed.), San Francisco. SOKAL, R. R. & P. H. A. SNEATH (1963). Principies of numerical taxonomy. San Francisco- London.